System Diagnosis: Notes

NOTE: Chrysler Motors recommends using DRB-II to diagnose system. Voltmeter usage has limited diagnostic capabilities but can be used if DRB-II is not available or if working on a Mitsubishi Motors vehicle.

The Engine Control Unit (ECU) monitors several different engine control system circuits. If an abnormal input signal occurs, a fault code is stored in ECU memory and given a fault code number. Each circuit has its own fault number and message. A specific fault code indicates a particular system failure, but it DOES NOT indicate that cause of failure is necessarily within system. A fault code DOES NOT condemn any specific component; it simply points out a probable malfunctioning area. If a critical fault code is set, the ECU will turn on CHECK ENGINE light. All fault codes except speed sensor are considered critical.

Fault codes can be confirmed by using a voltmeter on Chrysler Motors and Mitsubishi models or Chrysler's Diagnostic Readout Box (DRB-II) on Chrysler Motors vehicles. See ENTERING ON-BOARD DIAGNOSTICS (USING VOLTMETER) or ENTERING ON-BOARD DIAGNOSTICS (USING DRB-II) . By using the DRB-II, the self-diagnostic capabilities of this system can simplify testing and reduce diagnostic time.

System malfunctions encountered are identified as either hard failures or intermittent failures as determined by the ECU.